Electric discharge tube



July A6 1926.' 1,591,129 G. HOLST ET AL ELECTRIC DISCHARG; TUBE Filed Feb'. 18, 1925 Patented July 6, 1926.

UNITED STATES PATENT olElcE.

GILLES HOLST AND ALBERT DOUWE-RS, 0F `EINDHOVEN, NETHERLANDS, ASSIGNORS T0 N. v. PHILIPS GLOEILAMRENFABRIEKEN, 0F EINDHOVEN, NETHERLANDS.

ELECTRIC DISCHARGE TUBE.

Application tiled February 18, 1925, Serial No. 10,104, and vIletherlangls April 10, 1924.

This invention relatesto discharge tubes provided with an incandescent cathode and aving an envelope which consists partly of insulatin materlal such as, 'for exam le,

glass an partly -of metal, the insulatlng'` part being sealed to 'the metal part. The invention relates in tubes of this kind for high tensions, such as for example, X-ray tubes.

Discharge tubes, part of the outerv envelope of which consists of metal which is .sealed to the insulating part of the envelope, have the disadvantage that electric char es', giving rise to disruption of the insulatmg -material accumulate near the' seal of the envelope. Y

In order to obviate this disadvantage, it has alread been proposed to arrange in the neighbour ood of the `seal of the envelope a metal wall -which is electrically connectedto the anticathode and serves to prevent the electrons emanatin from the incandescent cathode, from reac ing the seal of the envelope.

According to the invention, a number of metal Walls which overlap each other, are insulated `from each other and receive different potentials during the operation of the to each other.

tube, are so arranged between 'the incandes- Acent cathode and the seal of the envelope that electrons emitted by the` incandescent cathode, would only be able to reach said seal after passing between the said walls.

The metal walls are preferably so arran ed that considerable parts .of them are para lel By supplying suitable potentials to the adjacent walls, care can be taken that practically' not any electron reaches theseal of the envelope. In discharge tubes for high voltages the metal walls are, preferably so arran ed that during the o eration of the tube t ere is a high potentia difference be-l tween adjacent walls. Y The invention maybe applied with special advantages to'X-ray tubes in which the incandescent. cathode is arranged within a metal. vessel formin wholly or partly part of the outer wall of t e tube, the anticathode being separated from said metal vessel by an insulation that is caplable of resisting the Aoperating voltage whic has to be supplied between the incandescent cathode an anticathode. Thisv metal vessel is so shaped particular to discharge' l that vthe cathode rays are capable of striking the anticathode only on a limited area.

cathode', the metal walls overlapping each other are, preferably, yalso coaxially arranged relatively to the metal vessel. l

' The accompanying drawing represents by way of example some constructiofl'is showing the application of the inventi'dn td an X-ray tube of the kind abovel described.

Figure l represents a longitudinal section of an X-ray tube in which the metal walls, provided according to the invention, are arranged coaxially tothe anticathode.

igure 2 is a longitudinal sect-ion of part ofja ldifferent construction, in which the walls overlapping each other are at right angles to the side face of the anticathode.

i, The outer wallaof the X-ray tube shewn in Figure 1, consists of an insulating part l, made, for example, of glass and of a metal part 2 being at l30 hermetically sealed to the glass part. On the other side the vessel .2 1s hermetically connected to a glass hood 3 which serves for Ythe passage ofthe X-ra s. An incandescent cathode 5, supported by leading-in wires 6 and 7, is arranged within, the Vessel 2. Terminals 8 and 9 serve to sup# ply the current to the incandescent cathode; the terminal 8 -is preferably connected to the negative pole of the battery for the currentl 0f incandescence. The leading-in wire 7 is connected to an angular bottom 10, fro'ni which the, wire 6 passing through said bottom is insulated. l

On the side of the anticathode 12 the metal vessel 2 is provided with a partition 11 hav- -the anticathode is coaxially arranged within the metal vessel enclosing the incandescent ing an aperture 13. Behind this aperture stretches the front face of an anticathode 12 which at- 14 is hermetically sealed to the insulating part l. Theanti-cathode may be cooled in any suitable manner, for which purpose a cooling tube 15 is provided.

During the operation of theX-ray tube, the electrons emitted by the incandescent cathode 5, are capable of striking only a small area of the front faceV of the anticathode owing tothe peculiar Ashape and the arrangement of the vessel 2 relatively to the l anticathode 12. The X-rays generated pass through the aperture 13, through an aperture 1-6 provided in the bottom 10 and through the glass hood 3.

lf in the X-ray tube according t'o Figure 1 there had not been taken special measures, electric charges would be capable of accumulating near the places of connection 30 and 14, which might have the known detrimental consequence-s.

According to the invention, there are provided overlapping walls 17 and 18 which lare arranged coaxially to the metal vessel 2 and to the anticathode and which form a kind of labyrinth packing. The wall 17 torins awhole with the partition 11, Whereas the wall 18 is electrically connected to the anticathode, to which itis secured by means of screws 19.

The electrons emitted by the incandescent cathode, would still be capable of reaching the places of connection 30 and 14 but only after passing between the walls -17 and 18. They will however be prevented therefrom by the strong electric fields occurring between the walls 17 and 18 mutually, between the wall 17 and the anticathode .12 and between the Wall 18 and the vessel 2.

The metal vessel '2 may advantageously consist of chrome iron `of suitable composition. The body of the anticathode 12 may also be madeof chrome iron, in which case an insertion piece of tungsten may be provided on the front face of the anticatliode.

Figure 24illustrates another embodiment of the invention. According to this figure overlapping Walls 2O and 21 are provided in order to prevent electrons from reaching the places of connection 22 and 23. -A' wall 20 is secured near the front face of an anticathode 24 and a. wall 21 is screwed into a. l`metal vessel 25 which forms part of the outer wall, the incandescent'cathode which 1s not illustrated, being arranged within said metal vessel.

1. An electric discharge tube with an incandescent cathode and an envelope consisting partly ot' insulating material and partly ot' metal, Whichinsulating part is sealed to the metal part, a number of metal walls insulated from each other Within the envelope andreceiving di'erent potentials during the opera-tion of the tube being so arranged as to form alabyrinth seal between the cathode as well as between the anticathode and the seal of the envelope.

2. An X-ray tube according to claim 1, in which the anticathode is arranged within a metal vessel which forms partvot the outer wall of the tube and from which thel anticathode is separated by an insulation that is capable of resisting the operating voltage to be supplied between the incandescent cathode and the anticathode, said vessel being so shaped .that the cathode rays can strike the anticathode only on a limited area, one ore more of the metal walls 'being electrically connected to the anticathode and one or more to the metal vessel. y

3. An X-ray tube according to claim 1.

which the anticathode is coaxially arranged within a metal vessel which forms part of the outer wall of the tube and from which the anticathode is separated by an insulation that is capable of resisting the operating voltage to be supplied between the incandescent cathode and the anticathode, said vessel being so shaped that the cathode rays can strike the anticathode only on a limited areafone or more of the metal walls, which extend coaxially between the anticathode and the said metal vessel, being electrically connected to the anticathode and one or more to the said metal vessel.

In testimony whereof'we aix our signatures at the city of Eindhoven this 26th day of January, A. D. 1925. l

GILLES HOLST. ALBERT BOUWERS. 

